It is generally recognized that combustion ability of certain heavy waste oil employed as furnace fuel may be improved by significantly pre-beating, vaporizing or pre-mixing such fuel with vaporized gases or other vapors prior to combustion. It is also understood, that in many cases a heating appliance itself does not provide sufficient heat to effect such fuel vaporization or similar fuel conditioning treatment, and therefore additional means, such as electric heating coils and the like, have to be installed in order to facilitate such conditioning or pre-combustion treatment of heavy waste oil fuels.
It is further known that such high temperature pre-heating and vaporizing treatment is especially useful to effectively reduce viscosity of such heavy fuel in order to render it at all usable, and a number of prior art disclosures describe various complicted methods and devices specifically developed for that purpose.
In U.S. Pat. No. 3,876,363, La Haye et al. discloses a method, which uses an external source of heat as well as part of the combustion chamber heat, to finely atomize a hydrocarbon fluid such as fuel oil to produce an emulsion of the oil with a secondary fluid prior to fuel oil combustion, thereby increasing combustion efficiency and minimizing pollutant discharge during combustion of such emulsified fuel mixture. For this purpose, the fuel is pre-heated to a temperature of between 150 to 250 degrees Fahrenheit.
In U.S. Pat. No. 2,840,148, I. W. Akesson discloses a furnace burner-blower arrangement, which employs pressure and heat to pre-treat heavy fuel oil prior to combustion. The fuel oil is heated by way of a heating element which is controlled by thermostats to maintain a certain oil temperature range, but without stating any specific and most advantageous operating fuel oil temperature range.
In U.S. Pat. No. 2,781,087, Peter Storti et al. disclose a rotary cup type, heavy oil burner system, which circulates the fuel through the burner on its way to the atomizer nozzle. This application further utilizes an electric heating device to pre-heat the fuel oil in a thermostatically controlled oil reservoir prior to combustion. This system presents a distinct improvement over other prior art, in that it greatly reduces the fuel oil temperature fluctuations inherent in other fuel pre-heating systems. However, no specific fuel oil operating temperature range is indicated to claim combustion efficiency or emission reduction.
In CA Patent No. 380,126, Andrew Palko discloses an oil burner comprising an electric heating element to pre-heat the burner so as to cause instant vaporization of the fuel oil as it is fed to the burner. This system includes temperature control means to regulate the fuel oil temperature without specifying any particular fuel oil temperature or temperature range, which would be required to obtain the claimed vaporization and desired combustion efficiency or emission reduction.
In CA Patent No. 457,123, Earl J. Senninger discloses an oil burner especially adapted for heavy oils. Such heavy fuel oils are pre-heated by way of an electric heating element prior to reaching the atomizing nozzle of the burner unit. Here the desired fuel oil operating temperature range is described as a temperature to be such as to insure against carbonizing of the fuel, which would normally be a temperature just short of combustion.
In U.S. Pat. No. 4,392,820, Niederholtmeier discloses a system for operating a heating appliance comprising the combination of unheated conventional fuel oil and pre-heated heavy waste oil in two separate pressure controlled distribution networks, precluding any intermingling of the two fuel sources. The waste oil is pre-heated to it's flash point level in order to reduce its viscosity and to render it combustible, and is fed to the burner after conditioning the burner by first operating it for a period of time with conventional untreated fuel oil, facilitating subsequent combustion of treated waste oil.
In U.S. Pat. No. 5,888,060 a method and device is disclosed to increase combustion efficiency of heating appliances. The disclosure is based on pre-heating hydrocarbon fuel to a moderate temperature level prior to combustion within a range of 37 degrees F. and the fuel's flashpoint temperature prior to the fuel entering the furnace flow valve. This results in reduced fuel flow instead of obtaining the effect of fuel injection.
For the purpose of creating a fuel injection condition for natural gas and propane gas, as well as for other conventional hydrocarbon fuels for use in appliances incorporating a burner located in a combustion zone, so as to increase fuel flow velocity and flame speed during combustion of such fuels in accordance with the present invention, a different set of circumstances is required.
In order to effect combustion efficiency and a noticeable reduction in harmful flue gas emission, an appliance burner will respond to fuel delivered to its burner nozzle at an increased velocity without causing the typical "blowout" condition. Such effect is obtained by decreasing the density of fuel while at the same time increasing the volume of the fuel by constantly and specifically elevating fuel pre-combustion temperature level. Such elevated temperature level must not be as high as to approach the flash point temperature of the fuel, as this would interfere with the function of the burner orifice, resulting in a loss of combustion efficiency, which would be contrary to the teaching in this disclosure In fact, the most advantageous fuel pre-combustion operating condition, according to the present invention, is to effect maximum fuel expansion and fuel volume increase and effecting fuel input velocity of the normally low temperature delivered fuel after the fuel has passed through the furnace operating valve, or a special one-way flow control valve, just ahead of the furnace orifice, without causing interference with the conventional combustion process of the appliance. This will create the effect of fuel injection without causing flame blowout during ignition.
During more frigid periods of the year, when heating appliances are usually in operation, fuel stored in storage tanks especially, and fuel transported in conduits exposed to the elements for considerable distances, remains at a temperature well below the optimal contemplated operating range, and pre-heating fuel economically could provide a number of significant advantages available for both gas and oil applications. Even appliances operating during the summer period, such as gas fired cooling appliances or residential, commercial and industrial water and process heaters, may operate more efficiently with the contemplated fuel injection method and device.
It is an established fact that most fluid hydrocarbon fuels may expand in volume by approximately 1% for each 5 degrees Fahrenheit of fuel temperature increase. Therefore, in a condition where such fuel is delivered to the burner mechanism at a low temperature, especially when reaching levels below 35 degrees Fahrenheit, fuel pre-heating, especially at a temperature reaching 900 degrees Fahrenheit would automatically result in a possible expansion of fuel volume of up to 180% while maintaining the same fuel mass.
Furthermore, such expanded fuel delivered to the burner orifice at its more optimal volume and flow velocity, but at the same fuel mass, would produce significantly more intense and complete combustion due to its higher flame speed and higher flame temperature, with the expanded lower density fuel allowing for a more rapid and complete fuel mix and advanced ignition. It creates the effect of fuel injection without the danger of flame blow-out, resulting in a measurable increase in burner efficiency as well as a measurable decrease in harmful flue gas emission. The fuel expansion must however be controlled by way of a special one-way valve such as to increase fuel flow velocity in the direction of flow only, wherein the increased fuel volume due to fuel pre-heating occurring just ahead of the orifice, results in a significant increase in velocity of less dense fuel through the burner orifice.
It therefore stands to reason that such a simple method and device, which provides an economical method for energy efficient fuel injection, increasing flame temperature and flame speed during combustion in an appliance by pre-heating of its conventional fluid hydrocarbon fuel just ahead of the burner orifice, would be most desirable.
Most prior art examined however seems to be specifically designed to treat only unconventional combustion fuels like heavy fuel oils or waste oils, and then in all cases, such prior art must rely without exception on additional heating elements to effect the temperature pre-heating process to the level of up to or above fuel vaporization or up to the flash point level of the fuel. This is of course contrary to the teaching disclosed in the present invention and outside the function of the method and device contemplated and described further herein, and there is no prior art available at all which teaches the pre-heat treatment of natural gas or propane gas for the purpose of causing the effect of fuel injection and increasing ignition and flame speed as well as general combustion dynamics in accordance with this invention.
Furthermore, it is still presently believed in the gas combustion appliance industry that pre-heating of fuel, as contemplated in this invention, is not affective to cause a fuel injection effect and thereby increase combustion dynamics. In fact, a correction formula is always employed in the industry to eliminate any variance in fuel efficiency calculations due to a change in fuel supply temperature or fuel density. Such correction formula calculation may be found in the "Gas Engineers Handbook", Ninth Printing, Chapter 8, "Gas Calorimetry", Pages 6-42.
Therefore, the method and device as disclosed in the present invention is completely contrary to industry norm, and is not at all obvious.